Phonograph



July 14,1942. l E. L. TRW/nlmr PHONOGRAPH Filed July 1'7, 1941 Patented July 14, 1942 PHGNOGRAPH Eugene L. Triman, Chicago, lll., ssiznor to Rock-Ola Manufacturing Corporation, cago, lll., a corporation of Delaware Chl.-

Appncaaon July 1v, 1941, serai No. 402,143

` (ci 17a-c) 8 Claims.

My invention relates to phonograph systems,

` and more particularly to a system forV electrically reproducing phonograph records wherein a central station serves a `plurality of subscribers stations. At the. present time, automatic phonograph have been provided with a larger number of phonograph records than washeretofore available. In `spite of the increase in the number of phonograph records now available inautomatic phonographs, it would be desirable if a still larger number of phonograph records could be provided. One manner of providing 'a greater number of records is to provide a central station which serves a number of subscribers stations. Obviously in such an arrangement it is highly desirable to provide such a system for use in `conjunction with the present automatic phonographs. In such systems the subscriber signals the central station operator, whereupon the operator inquires from the subscriber as to what selection or selections are desired. It is desirable in such systems to simplify the telephone apparatus utilized as much as possible, and hence it is preferableV to use a single channel system between the subscriber station and the central station. However, in such an arrangement it is desirable to provide some arrangement for preventing the subscribers voice from `being repeated in the loud speaker provided at the subscriber station. In accordance with my invention certain ligure `is duplicated for each subscriber installation. Since it furthermore is desirable to utilize such systems in conjunction with existing automatic phonographs. certain elements shown in the Iilgure have been enclosed within dotted lines to indicate that these elements may be commonly found in existing automatic phonographs.

Thus a phonograph of the automatic type is provided with a phonograph turntable and motor I I which cooperates with a phonograph pickup l2, illustrated herein as being of the piezo crystal type. 'I'he phonograph pick-up I2, when utilized in the` conventional automatic phonograph, is connected through an adjustable resistor I3, a switch I4, and resistors I5 and I6 to an amplifier I/l which is connected to a sound reproducen-oi' loud-speaker I8. Such phonographs are. furthermore, provided with a coin chute or switch I9 which normally would be connected through a switch 2| to an accumulator relay 22 which is energized by means of a transformer 23- from a suitable source of alternating current 24. The elements just described, including the amplifier, may be of the type shown and of these desirable advantages not found in the I prior art may be had with a minimum of `equipment. f

It is, therefore, an object of my invention to provide an improved system for electrically reproducing phonograph records.

Still another object of my invention is to provide in a phonograph system a new and improved arrangement for preventing the outgoing signal from being reproduced by the incoming signal reproducer. v y

Still another object of my invention is to provide an improved circuit arrangement for discriminating between incoming and outgoingsignals.

Other and further objectsl of my invention will become more readily apparent from the following description taken in\ connection with the accompanying drawing in which the figure is a. circuit arrangement for electrically reproducing vvphonograph records in accordance with my invention.

Referring more particularly to the drawing, there is shown in the figure, a circuit arrangement such as is utilized between each subscriber station and the central station. While only one such circuitarrangement has been shown, it, of course, is to be understood that the central station is to provideservice for a plurality of subscribers and that the equipment shown in the illustrated in the United States Letters Patent No. 2,159,834, granted May 23, 1939, upon the application of Paul H. Smyth.l Jr., and which is as,- signed to the same assignee as the present application.

Each of the switches I4 and 2l is a single-pole, double-throw` switch, and these switches are preferably mechanically connected together so that they may be operated by a single operation. When these switches are thrown to the right, the automatic phonograph operates as a conventional phonograph. When these switches are thrown to the left, those elements of the automatic phonograph shown in the ligure become a part of the system for electrically reproducing phonograph records.

When the switches I4 and 2l have been thrown to the left, the subscriber inserts one or more coins into av coin chute thereby operating the Acoin chute or switch I9. Since the switch 2l has been thrown to the left.` this coin chute I9 is now connected in series with `a relay coil 25 and a capacitor 26. The capacitor 26 is arranged to be charged from a suitable source of uni-directional current which may comprise one or more electric valves or rectiers 21 which are energized from the transformer 23. The transformer 23 and the'rectifler 21 serve to supply uni-directional current impulses to the capacitor 26 thereby to store energy therein. The transformer 23 is preferably of a type having a relatively high impedance, or in other words, a poor regulation characteristic, so that during the time that the capacitor 26 is being charged the voltage supplied by the transformer 23 is relatively high. When the coin switch I9 is closed, the discharge of the transformer 26 produces a heavy initial pull on the relay coil thereby insuring the positive operation of the switch contacts controlled by the .relay coil. At the same time, because of the poor regulation characteristics of the transformer 23, the uni-directional current impulses supplied by the rectifier elements 21 are of a low voltage, and hence. these impulses do not have any detrimental effects upon the relay coil 25. The relay coil 25, however, is provided witha copper ring or slug in a manner similar to the construction of alternating current relays, and hence forconvenience, this relay will be termed an alternating current relay. Whenever the relay 25 has been energized, normally closed switch contacts 28 and 29 are opened and normally open contacts 3l and 32 are closed. 'I'he closing of the contacts 3| and 32 connects a transformer 33 to an output transformer 34 which is connected to a suitable telephone line 35 connecting the subscriber station to the central station. The transformer 33 is an isolating transformer which may be energized from a suitable source of pulsating or alternating current such as the source 24. In order that the current transmitted over the telephone line be of a frequency which corresponds solely to the frequency of the source of current 24, the contacts 3l and 32 are so arranged that the altemating current supplied by the transformer 33 is connected through suitable alternating current filter means such as choke coilsv36 and 31. At

, the same time that alternating current is supplied to the telephone line 35, an alternating current relay 33 is energized to open a pair of normally closed contacts 39 which serve to disconnect certain apparatus from the contacts of the relay 25 whenever alternating current of the frequency supplied by the transformer 33' is being transmitted over the telephone line to the central station.

The alternating current impulses transmitted to the central station which correspond in number to the number or the value of the coins inserted in the coin chute I9 also serve to signal the central station operator, who then communic ates with the subscriber to determine as to what selection or selections are desired. The central station operators voice is transmitted over the telephone line 35, through the transformer 34, through normally closed contacts 28, 29 and 39, and through certain apparatus interconnecting these contacts with the amplier I1 and to sound reproducer I8. Certain of these elements interconnect both the sound reproducer I3 and a subscriber microphone 4I and the amplier therefor 42 with the telephone line.

The one side of the telephone line which is connected through the contacts 28 and 39 is connected through a loss pad 43 to one side of the amplifier 42 which serves to amplify the energy received by the microphone 4I. The other side of the telephone line which is connected through the contacts 29 is directly connected to the other side of the amplifier 42. The transformer 44 is connected to the telephone line between the contacts 29 and 39. The output winding of the transformer 44 is provided with an adjustable resistor or voltage divider 45, the movable contact of which is connected to an electric valve 46. 'I'he output of the electric valve is connected in parallel with the output of a. second electric valve 41 and the outputs of these valves are connected to a transformer 48, which in turn is connected through an attenuator 49L a transformer 5I to the switch I4, which in turn is connected through certainelements to the amplifier I1 and the sound reproducer I8. The electric Valve or vacuum tube 46 is arranged so that its input circuit is energized from the transformer 44 through the voltage divider 45. The input circuit for the electric valve 41 is energized from a loss pad 52 .which is connected across the output circuit of the amplifier 42. As shown in the figure, the loss pads 43 and 52 have been represented as T-pads utilizing a plurality of resistors. It is to be understood that any other form of loss pad, such as the L or H types, may be utilized, and furthermore, may use other components besides resistor elements.

The circuit elements comprising the loss pad 43, the phase inverter transformer 44, the voltage divider 45, the electric valves 46 and 41, and the loss pad 52 comprise a. circuit which operates to dierentiate between incoming and outgoing signals. By so differentiating between incoming and outgoing signals, the outgoing signal from the amplifier 42 is prevented from affecting the sound reproducer I8. The signal from the amplifier 42 divides at the output thereof so that a portion passes through the loss pad 43, and another portion passes through the similar loss pad 52. The currents passing through the loss pad 43 are inverted by the phase inverter 44 so that, with respect to the input circuit of the valve 46, these currents are opposite in phase to the currents appearing across the input circuit to the valve 41. By suitable adjustment of the voltage divider 45, these currents can be made to neutralize each other in the common output circuit so that no currents will affect the sound reproducer I8. Incoming signals from the telephone line 35, however, will not be of equal amplitude with respect to the input circuits of the valves 45 and 46, since the incoming signal passes directly through the transformer 44 to the input circuit of the valve 46. A portion of the incoming signal passes through the loss pad 43 and also the loss pad 52 so that the signal energy appearing across the input circuit of the valve 41 is much less, and hence, in the common output circuit of these valves these currents are not neutralized. Thus the incoming signal affects the transformer 48 so that it Vis transmitted through the attenuator 49, the transformer 5I, the resistor elements I5 and I6 to the amplifier I1 thereby actuating the `sound reproducer I8.

The telephone line 35 is connected to the telephone central by means of a suitable isolation transformer 53. Alternating current impulses received from the subscriber station over the telephone line 35 through the transformer 53 are received by a circuit, called a coin impulse detector circuit, comprising a capacity 54 connected in series with a rectifier 55, and which are connected across one of the windings of the transformer 53, and a second rectifier 56 reversely connected with respect to the rectifier 55 which is connected from one side of the rectifier 55 to the juncture between the rectifier 55 and the capacitor 54. The connection between the rectifier 56 and the juncture between the capacitor 54 and the rectifier 55 may be termed an output circuit for the coin detector circuit and this output circuit is connected to a relay 51 which is provided with a pair of contacts 58 connected in series with a suitable source of power 59 to energize a subscriber play indicator 6 I. The subscriber play indicator 6I serves to call the operator whenever a subscriber inserts a coin in the coin chute, and furthermore, indicates t e total number of coins, or alternating current inrpulses received from the subscriber station\ The central station is provided with a microphone 82, an amplifier thereforv 83 and a sound reproducer or headphone 84 vwhereby the central station operator may communicate with the subscriber inorder to determine what selection or selections are desired. The microphone 82 and the sound reproducer 84 constitute parts of outgoing and incoming signal channels, respectively, which are maintained separately by means of a channel differentiating circuit similar to that used at the subscriber station.

A circuit for differentiating between incoming and outgoing signals is connected through an isolating capacitor 85 to one winding of the transformer 83. The circuit comprises a filter section 88 connected between `the capacitor 88 and the output transformer 81 of an amplifier 88 which serves to amplify energy received from the microphone amplifier 83 and also energy received from a phonograph pick-up 88 which cooperates with a phonograph turntable and motor 1I. A second filter section or loss pad 12, similar to the filter or loss pad section 88 is connected to the incoming and outgoing telephone channel and to the input circuit of an electric valve 13, the output of .which is connected to a transformer 15. A transformer 18 is connected across the incoming and outgoing telephone channel and the secondary winding thereof is provided with a voltage divider 11 which is connected to the input circuit of an electric valve 18. The output circuit of the electric valve 18 is connected in parallel with the output circuit of the electric valve 13 to the transformer 15. The remaining winding of the transformer 15 is connected to switch blades 18 and 8| of a talk-listen switch 82. The switch blades 8l and 18 when operated are connected to the sound reproducer or head-phone 84. w

The microphone 82 and the amplifier 83 are connected Ato the switch blad: 83 and a switch blade 84 of the talk-listen switch 82 so that when the switch is actuated the output of the amplifier 83 is connected to the input circuit of the electric valve 88 through a resistor 85 which is connected to the control electrode or grid of the amplifier tube 88. amplifier 83 is connected to the cathode of the tube 88 which is provided with a suitable cathode resistor 88 so that whenever energy is received by the vacuum tube 88 the central station operator's voice will predominate over the sound being reproduced from a phonograph record by means of a phonograph turntable and motor 1I and the phonograph pickup 88. Interposed between the phonograph pick-up 88 and the input circuit to the amplier tube 88 is a circuit for compensating for the attenuation of certain frequencies which occurs during the transmission of the energy from the central station to the subscriber station. This circuit comprises a capacitor 88 connected in parallel with a resistor 81 which serves to compensate for the attenuation of the high frequencies. A capacitor 88 and a resistor 88 connected between the ground terminal of the phonograph pick-up 88 and the cathode resistor 88 ofthe amplifier tube serve to compensate for the attenuation of the low frequencies. kA capacitor 8l is connected between the movable contact and one end of a voltage divider 92 which serves as a volume con- The other terminal of the trol means. The capacitor 9| is so selected as to compensate for the attenuation of the middle range of frequencies to be transmitted.

Upon receiving one or more coin impulses at the central station, the coin impulse detector comprising the capacitor 54 and the reversely connected rectifier elements 55 and 58 energizes the relay 51 to operate the subscriber play indicator. This subscriber play indicator is usually provided with a signal lamp which calls 'the attention of the operator, and furthermore, is provided with a dial indicator showing the total number of impulses received. The central station operator, upon noticing the signal of the subscriber play indicator 8l, actuates the switch 82 thereby connecting the microphone 82 and the headphone 84 to the telephone line 35 through the incoming and outgoing channel differentiation circuit. This circuit comprising the loss pads 88 and 12, the electric valves 13 and 18, the phase inverter transformer 18, the voltage divider 11 and the transformer 15 preventing the energy from the microphone 82 from being reproduced in the headphone or sound reproducer 84.

When the central station operator speaks into the microphone 82 to inquire as to what selection or selections are desired, the energy therefrom passes through the amplifier 83 and the amplifier 88 to the loss pad 88 and on to the telephone line 35. A portion of this energy also passes through the loss pad 12 which is connected to the input circuit ofthe valve 13. Furthermore, a portion of the outgoing energy also passes into the phase inverter 18 which is connected to the input circuit of the valve 18. The input circuit of the valve 18 is so adjusted by means of the voltage divider 11 that the energy of the outgoing signal received `by the input circuits of the valves 13 and 18 are neutralized in the common output circuit of the valves which is connected to the transformer 15. Signals being received from the subscriber station over the telephone line 35, however, are not neutralized in the output circuit of these valves since the energy comes in directly to the input circuit of the valve 18 through the phase inverter 18. The energy, in order to reach the input circuit of the valve 1.3, however, must pass through the loss pad 88 and the loss pad 12 which so attenuate the energy that no neutralization of the signal can occur in the common output circuit of these valves.

From the foregoing description of the circuit arrangement and the operation thereof, it will become apparent to those skilled in the art that it is possible to arrange at each end of the telephone line or at only one end thereof a circuit which differentiates between incoming and outgoing signals so as to separate these signals into two channels. In the arrangement shown, it will be readily apparent that it is very desirable to prevent the highly amplified outgoing signal from affecting the sound reproducer at that location. It, furthermore, will be apparent that, while the loss pads utilized in this circuit have been shown as being of the T-type, other types of loss pads may be utilized.

While I have shown and described my invention as illustrated in but a single embodiment, and have shown its application to a particular circuit arrangement or system, it is to be understood that modifications may be made in the circuit arrangements and in the instrumentalities employed therein without departing from the spirit and scope of the appended claims.

What I claim as new and desire by.

a plurality of subscribers stations each con-- nected thereto by a two wire telephone line, means located at each subscriber station including a microphone and a sound reproducer, means located at said central station including a phonograph pick-up, a microphone, and a sound reproducer, circuit means at each end of said telephone line for interconnecting said means with said line, said circuit means having a two-way channel connected to said line, a one-way channel connected to said sound reproducer, another one-way channel connected to a microphone, a loss pad connected between said microphone channel and said two-way channel, and a second loss pad connected between said microphone channel and said sound reproducer channel, and a phase inverter connected between said twoway channel and said sound reproducer channel.

2. A system for electrically reproducing phono- I graph records comprising a central station and a plurality of subscribers stations each connected thereto by a two wire telephone line, means located at each subscriber station including a microphone and a sound reproducer, means lo- -cated at said central station including a phonograph pick-up, a microphone, and a sound reproducer, circuit means at each end of said telephone line for interconnecting said means with said line, said circuit means having a two-Way channel connected to said line, a one-way channel connected to said sound reproducer, another one-way channel connected to a microphone, a loss pad connected between said microphone channel and said two-'way channel, a second similar loss pad connected between said microphone channel and said sound reproducer channel, and a phase inverter connected between said two-way channel and said sound reproducer channel whereby energy from said microphone channel is balanced out of said sound reproducer channel, said central station phonograph pick-up having a common channel with said central station microphone.

3. A system for electrically reproducing phonograph records comprising a central station and a plurality of subscribers stations each connected thereto by a two-way telephone line, means for electrically reproducing phonograph records comprising certain elements located at said central station and other elements located at each subscriber station, said latter elements including a sound reproducer and a microphone for communication with said central station, and circuit means for preventing energy from said microphone from being reproduced by said sound reproducer comprising a loss pad connected between said microphone and said telephone line, a second similar loss pad connected between said microphone and said sound reproducer, a phase inverter connected between said Iline and said sound reproducer, and a pair of electric valves having a common output connected to said sound reproducer, the inputs of said valves being respectively connected to said phase inverter and to said second loss pad.

4. In a communication system, the combination of a telephone line, an input lchannel and an output channel associated with each end of said line, and circuit means interconnecting said u Vchannels/with the ends of said line each comprising a loss pad connected between said line and said input channel, another similar loss pad connected between said input channel and said output channel, and a phase inverter connected between said line and said output channel,

5. The combination with a telephone line comprising a phase inverter connected to said line, a resistance illter section connected in said line. a communication channel connected to said filter section, a second similar nlter section connected to said line, a one-way channel, a pair of electric valves having their outputs connected in parallel to said latter channel, means connecting the input of one oi' said valves to said phase inverter, and means connecting the other of said valves to said second tilter section.

6. The combination with a pair of electric conductors comprising a microphone, a sound reproducer, a iilter section connected between said microphone and said conductors, a phase inverter connected to said conductors, a second similar iilter section connected to said microphone, a pair of electric valves having a. common output connected to said sound reproducer, means connecting the input of one of said valves to said phase inverter and means connecting the input of the other of said valves to said second illter section whereby energy received by said microphone will not be reproduced by said sound reproducer.

7. In a communication system, the combination of a ltwo wire telephone line, an input channel and an output channel associated with each end of said line, and means interconnecting said channels with the ends of said line each comprising an impedance connected between an input channel and one side of said line, a pair of controlled electric valves having their cathodes connected to the other side oi.' said line and their anodes connected to an output channel, phase shifting means connected between an end of said line and the input to one of said valves, and a second similar impedance connected between the input to the other ofrsaid valves and the Juncture of said iirst impedance with said input channel.

8. The combination, in a communication system, of a two wire telephone line, an input channel including a microphone, an output channel including a sound reproducer, a pair of like impedances each having one terminal connected to the same side of said microphone, one side of said telephone line being connected to 'the other end of one of said impedances, the other side of said telephone line being connected to the other side of said microphone, a pair of controlled electric valves having their cathodes connected to said latter side of said telephone line, said output channel being vconnected between said latter side of said telephone line and the anodes of said valves, means connecting the control electrode of one of said valves to said sccond impedance, means connected across said telephone line to produce a phase inversion with respect to energy appearing across the inpuft of said mentioned valve connected to said impedence, and means for supplying to the control electrode of said other valve a predetermined portion of the energy supplied by said first inversion means.

EUGENE L. TRIMAN. 

